1. Field of the Invention
The present invention relates generally to a fiber optic receptacle for interconnecting optical fibers within a communications network, and more specifically, to a fiber optic receptacle that provides improvements in freeze/thaw cycle performance, sealing and connector alignment.
2. Description of the Related Art
Fiber optic networks are currently revolutionizing the telecommunications industry due to their high bandwidth carrying capacity, low signal degradation and low power usage. As a result, fiber optic networks are being created and expanded to deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), “fiber-to-the-premises” (FTTP) and “fiber-to-the-subscriber” (FTTS), referred to generically as “FTTx.” In order to provide services to one of these subscriber locations, fiber optic networks must include a large number of interconnection points in which optical fibers are optically connected or mated in the field. In the most recently developed fiber optic networks, communications service providers are demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” systems, that are robust enough for use in field applications. Plug-and-play systems allow less skilled field technicians to readily perform optical interconnections, thereby reducing field labor costs and the time required to install and activate optical networks.
Factory-prepared interconnection solutions should not only properly align mating optical fibers, but should also protect the mating optical fibers against adverse environmental and mechanical influences, such as from moisture intrusion and tensile forces, and more particularly, protect the receptacle assembly (i.e., alignment sleeve, etc.) at which the optical fibers are interconnected. Conventional fiber optic receptacles include a receptacle housing defining an internal cavity that houses an alignment sleeve for aligning opposing optical connectors or opposing ferrules. The alignment sleeve is typically inserted from the front-side of the receptacle and is designed to receive a pair of ferrules, each of which is mounted upon the end portions of one or more optical fibers. The alignment sleeve assists in gross alignment of the ferrules, and ferrule guide pins or other alignment means assist in detailed alignment of the optical fibers positioned on the end faces of the opposing ferrules. One of the ferrules is attached to the ends of one or more optical fibers extending from a cable, ribbon or optical fiber device and routed to the back-side of the receptacle, such as from the interior of a conventional optical connection terminal or closure. The other ferrule is mounted one or more optical fibers terminating in a fiber optic plug that is routed to the front-side of the receptacle, for example a connectorized drop cable leading to a subscriber of the optical network.
In the process of mating the opposing ferules within the receptacle, the plug ferrule is inserted into one end of the alignment sleeve. Original receptacle designs required that the plug ferrule be retained within the alignment sleeve by mechanical coupling, such as by means of a pair of latches. While the latches effectively secure the plug ferrule within the alignment sleeve, mechanical coupling disadvantageously limits float between the plug ferrule and the alignment sleeve. Recent receptacle designs include a biasing member, for example one or more linear springs, for providing float. In testing these receptacle designs, it has been determined that the biasing springs are subject to deformation during loading and ferrule insertion. To prevent this, structural design changes are needed to control spring travel and thereby prevent buckling. A new design is also needed to facilitate assembly by allowing for a “loose” fit between the biasing springs and the guide structures, and between the biasing springs and the bores into which the biasing springs are inserted. A receptacle design that controls spring travel, prevents buckling and provides for a loose fit would prevent damage to the biasing springs during assembly and use.
A possible advantage associated with existing receptacle designs is that they allow access to the alignment sleeve and the back-side (i.e., internal) ferrule from the outside of the connection terminal or enclosure without entering the connection terminal or closure, referred to herein as “external access.” To accomplish this, the receptacle is designed in two pieces as viewed from the front-side (i.e., external) side of the receptacle with the alignment sleeve held within the receptacle housing (first piece) by a second piece that is attached to the first piece and removable from outside the connection terminal or closure. An example of such an external two-piece design is the fiber optic receptacle described and shown in U.S. Pat. No. 6,579,014 entitled Fiber Optic Receptacle, which is assigned to the assignee of the present invention. However, such an external two-piece design requires an extra seal between the first piece and the second piece to prevent water ingress. Furthermore, the seal must be sufficiently strong to prevent connector failure due to freeze/thaw cycling that causes the second piece to separate from the first piece. In addition, an external two-piece design requires strict control and maintenance of high-quality molded surfaces. As previously mentioned, the external two-piece design provides a field technician with access to the alignment sleeve and the back-side ferrule. Accordingly, while it is advantageous to eliminate the external two-piece design and extra seal, an external one-piece design also eliminates the ability to access the alignment sleeve and back-side ferrule from the front-side of the receptacle. However, an external one-piece design permits the receptacle assembly to pass freeze/thaw cycle testing and provides further improvements with respect to ferrule and optical fiber alignment, which is especially important when mating angled physical contact (APC) connectors for low-loss requirements.